The present proposal is a longitudinal study of 135 elderly men and women who were first studied years earlier. The initial data indicated that among healthy individuals, aged 55-79 years, with relatively low blood pressures, 24-hour ambulatory blood pressure and heart rate (both level and variability) were significantly related to cognitive tests and signs of subtle brain damage as assessed by magnetic resonance imaging (MRI). The primary goal of this follow-up study is to demonstrate how ambulatory blood pressure technology can be useful in predicting future changes in brain and cognitive function which may be associated with apparent clinical problems but predate stroke and other cerebrovascular pathology. We will look at blood pressure and heart rate level and variability during two entire 24-hour periods, focusing on variability and level during wake and sleep, and the amount of fall from wake to sleep. In order to determine changes that have occurred, many procedures will be repeated, including a complete medical exam, casual blood pressure and heart rate measurement, and neuropsychological testing (sampling such critical areas as memory, attention, abstract reasoning, and cognitive flexibility. From MRI data we will determine both focal (T2 hyperintense lesions) and non focal (atrophic) brain changes. On the basis of our current findings, we expect that with the passage of time those individuals with higher casual and ambulatory blood pressure, greater blood pressure variability, and a smaller drop in blood pressure and heart rate during sleep will be likely to exhibit decrements in neuropsychological test performance and increases in T2 hyperintensities and brain atrophy. The fact that healthy, elderly individuals with normotensive blood pressure levels may be at risk for cognitive deficits and brain damage has clear implications for decisions regarding the appropriate level and variability of blood pressure to treat in elderly. Also, there is a need for future studies to concentrate on drug and behavioral methods which decrease variability of blood pressure and maintain 24-hour blood pressure control, in addition to decreasing casual blood pressure.